Electrode supporting structure



SPt- 8, 1931- R. HARDING. JR I 1,8229732 ELECTRODE SUPPORTING STRUCTURE Filed March 13, 1930 INVE TOR Reefer wp/NG .ne

AWORNEY Patented Sept. 8, 1931 t l Uurren stares 'PATENT CFFICE ROBERT HARDING, JR., O3? 'WHITE PLANS, NEW'YORK, SSIGNOR TO ARCT'UR'U'S RADIO v TUBE COMPANY, OF NETWARE, NEW JERSEY, Al CORPORATGN OF DELAWARE ELECTRODE SU'PPGRTENG STRUCTURE Application lfiled. March 13 This invention relates to electron-emitting devices of the type shown as thermionic vacuumtuhes, and more particularly to tubes of the type employing an electrode Which is 5 heated by direct heat transfer thereto from an independent source of energy, such as a filament or the like. The invention is an improvement on the type of device shown and described in the application of Walter L. Krahl, entitled: Radio receiving system, Serial Number 287,720, filed J une 23, 1928.

The invention contemplates the provision of a tliermionic tube so constructed as to permit the use of ordinary household or iiuctuating lighting current as a source f power for heating the electrode to electron-emitting temperatures.

An additional object of the present invention is to provide a thermionic tube which is adapted to operate on such a current for electrode exciting purposes, the output of Which is independent of fluctuations in the current.

Yet another object of the invention is the provision of a thermionic tube which is free A of hum, a deficiency Which usually 'exists in suchV devices when employing currents of commercial frequency.

A still further object of the invention is the provision of a tube of thecharacter` described, which employs the usual .four electrode elements in conjunction with the usual base contacts so arranged as to engage the contacts of a standard socket so that the tube may conveniently be plugged into a conventional radio receiving and amplifying apparatus Without modilication of the internal Wiring of such apparatus. Convenienceof arrangement of parts, simplicity and comparative ineXpense of manufacture, are further des sirable features that have been borne in mind -in the production and development of the invention.

The above objects are generally associated with the invention, but the specific objects will be set forth more in detail. In thermionic ency to become permanently deformed when 1930. serial 1in. 435,413.

the tube is subjected to rough treatment in the process of packing or When thetube is mishandled. Ordinarily, during the process .of manufacture of such tubes before the electrode assembly is inserted into the bulb and g vacuum applied to the same., the respective elements of the .tube are carefully spaced from each other in proper li'uxtaposition to insure maximum efiiciency of the tube. Any irregularity in the construction of the elements or any deformation of the same is usually corrected just prior to the insertion of the assembly into the bulb. However, if the assembly is placed Within the bulb and sealed therein, it is practically impossible for any subsequent deformity existing in the same to be corrected.

Tubes of this class are ordinarily provided with an anode in the form of a cylindrical plate, a control electrode in the. form 0f a vcircular grid, a cathode in the form of a cylindrical tube mounted vWithin the grid, and a central heater in the form of a resist ance unit or filament extending through the cathode. Proper operating conditions necessitate an assembly ofy these elements in which the heater, cathode, grid and anode are positionedvery close to each other. Due to the fact that each of these elements must be supported solely from a single base, and must extend Vupwardly from this base a considerable distance, great care must be exercised in inserting the assembly Within the tube so that the heater maintains its spaced position from the cathode, and so that the cathode and grid in turn remain spaced from the anode. lt frequently happens, however, that due to rough treatment of the bulb, the heater element comes into contact with the cathode, thereby causing a short circuit Which materially affects the operation of the tube. The occasion of such short circuiting is obvious by virtue of the close spacing of these elements, and the relatively remote source of support for the same.

In addition to the likelihood of short circuiting as caused by handling of the tubel or y any other outside influence, short circuiting may occur by virtue of inherent construction of tubes of this type. Such v.a condition 55 line 4-4 of Fig. 3;

may occur by virtue of the present day arrangement Which is employed for supporting the top of the cathode in spaced relationship to the heater element. In actual practice it has been found that when the cathode becomes heated the coefficient of expansion of the material from which the cathode is made becomes appreciable in its effect on the tube. Because it is customary to support cathodes of this type by a rigid Wire rod Which extends upwardly around the outside of the electronemitting assembly and by a strap, one end of which contacts With the cathode and the other end of which is secured to this rod, the relatively high temperature of the cathode and the relatively lovv temperature of the supporting structure which receives no heat from the'heater causes unequal expansion of these elements. Because the cathode is rigidly supported by this metal strap which ordinarily is unbendable vertically, the cathode in Order to compensate for its linear expansion, assumes curved form and in such a case it frequently happens that the cathode Will contact with the heater element at its central portion or at one or another of its extremities. The present invention contemplates a remedy for such a condition by providing a cathode support which Will permit linear expansion of the cathode Without any subsequent deformity of the same, thereby assuring proper spacing of the cathode and heater at all times.

Furthermore, the invention contemplates the provision of a support for the cathode Which is sufficiently rigid as to prevent relative movement of the cathode with respect to the heater when the tube is subjected to rough treatment, yet Which is sufficiently iexible in one direction as toY permit longitudinal expansion of the cathode. n

ln addition to provi ling a novel support for the cathode, the invention contemplates the provision of a novel supportfor the heater which Will maintain the same at all times spaced from the cathode and which Will per'- mit linear expansion thereof. Y

With these and many other objects in view which will more readily appear as the nature of the invention is better understood, the same consists in the novel construction, combination and arrangement of parts shown in the accompanying single sheet of drawings, in Which: Y Y

Fig. 1 is afront elevation of my improved electron-emitting device, certain parts being broken away to more clearly reveal the nature of the invention;

lFig. 2 is a detail rear view of the electronfemitting assembly; v

Fig. 3 is a top plan view of one form of the improved assembly;

Fig. 4 is a sectional view taken along the which is preferably formed of glass and is of the usual elongated tubular shape.

In the present invention, use is made of the usual four element tube adapted to op-v crate on alternating current, as described in the above-mentioned application and in Which the heater is substantially enclosed by the cathode. -Accordingly, the anode is shown at 17. This anode is preferably in the form of a cylindrical plate supported at opposite sides thereof by a pair of upstanding rods 2O and 22 respectively, having their ends embedded in a press 23. Designated at 18 is a control electrode in the form of a grid 19, supported on a rod-24 held in fixed position by a rod 2G secured in the press 23. A cathode is shown at 28. This cathode may be in the form of a. tube of nickel or of any other suitable metal having a coating of a substance which possesses high electronemitting properties when heated. Vhile the coating may be of any suitable material, it is preferably formed of a mixture comprised 0f oxides of barium or of strontium, or of both, which substance when heated is characterized by the fact that it has electronemitting properties.

The heater for the cathode' is shown'at 32 and is separate therefrom. This heater consists in a iilamentfextending coaxially Within the cathode. The heater is supported at its lower end by'a pair of extensions 38 and 40 Welded or otherwise'secured to vertical rods 42 and 44 having their lovver ends embedded in the press. While this heater may be formed Yin any suitable manner or of any suitable material, it is preferable that the same be constructed of tungsten, tantalum or any desirable element possessing a sufficient degree of durability and having suiiicient resistance to become incandescent and impart heat to the cathode.' This filament or heater may be covered by an insulating material, and while this material may be formed of any substance possessing insulating qualities; it is preferable to form the same of a substance such as a compound of aluminum trioxide on account of the facility with which such a substance may be coated onto the filament. Designated at 43 is a xed support in the form of a glass bead rigidly mounted on and suspended-from the press 23 by a supporting rod 42. While this bead may be of any suitable shape, it is shown in the present instance as being in the form of a solid cylindrical rod formed of an insulating material such as glass, having its ends supported by extensions 41 and 45 carried on the rods 2() and 22 respectively, which also support the anode 17.

As clearly shown in Fig. 3, the fixed bead is provided with a plurality of upstanding supporting members 50, 52, 54, and 56, the members 50 and 54 having secured thereto at their upper ends a U-shaped yoke member 60 formed of spring wire, having parallel arms 62 and 64 respectively. This yoke member is connected at 66 to the heater 32, the upper end of which it sup-- ports against lateral movement. The connecting means between the resilient yoke member and the heater 32 is in the form of a small metal hook 33 which is welded to the yoke member 60 at 33 and whichl extends beneath the heater 32 and supports the same under tension. The rod 52 has its upper end bent laterally as at 68 to provide a support to which is welded or otherwise secured a metal strap 70. The outer end of the strap 70 is in the form of a ring 72 in which is secured the upper end of the cylindrical cathode 78, whereby the same is supported against lateral movement and is at all times maintained in spaced relation to the heater element 32. Both the yoke member 60 and the strap 7() are flexible and have freedom of movement in a vertical plane. However, by virtue of the spaced supporting of one of these members and of the comparatively great width of the other, they are restricted from lateral movement, and since each of these elements serves to support the upper end of the electrodes, these electrodes are permanently held out of contact with each other. Theupper end of the rod 24 supporting the control electrode or grid 18 is secured in spaced position with respect to the cathode by means of a strap 73 welded or otherwise secured to the vertical rod 56 secured in the bead 43.

From the above arrangement of parts it will be seen that the electrode elements of the thermionic vacuum tube are all held in spaced position with respect to each other both at their upper and lower ends. l/Vhile there is a certain amount of difficulty encountered in maintaining'theanodeinspaced positionwith respect to the control electrode or grid, and while there is also a certain amount of danger involved due to the tendency of this latter member to come into contact with the catho de, the greatest peril involved in the manufacture of tubes of this type lies in the tendency of the heater element to contact with the Cathode element when the latter element becomes expanded due to heat. The present invention 'provides a means whereby longitudinal ex- 'p-ansion fof eithery thefcatlf1del`-e A for heater elefment iis ifrcely' permitted and wherebywthe Esame rn ay ioccur "without lateral distontiien y:of A'eiftlfieroftheseelements.y' i i themeelvififerl*r forrn'oif thel inv `airran-gamenit for accomplishing the same. resulrtvis"sla-own.y 'Yilhillethe"vgeneral method of supporting the heater elements has been retained in this modification, a two-point sus- ,l

direction but not in a horizontal direction.

The outer end of the yoke member 70 is bent to provide an annular collar 76 which is firmly secured to the upper end of the cathode. Thus the cathode is prevented from moving laterally when expansion occurs, the expansion being automatically taken care of by the flexibility of the arms 72 and 74. It is obvious that I have provided a device which will maintain a plurality of electrodes secured in their respective spaced positions within.

the tube, and one which will permit of axial expansion of these electrodes but which at the same time will prevent lateral movement of these elements with respect to each other.V

I am aware that heretofore filamentary electrodes have been placed within a thermionic tube in such a manner as to be freelyV expandable when heated, but I believe the provision of a non-filamentary electrode which may expand freely when heated within a thermionic tube to be novel.

I do not desire to limit myself to the exact y arrangement of parts shownandV described in this specification and drawings, as 1t 1s obvious that various modifications of the device are contemplated. Only insofar as the invention is particularly pointed out in the appended claim do I desire to be limited.

Having thus described my invention, what I claim is:

In a thermionic tube having a cathode and a heater therefor extending coaxially therewith, means for supporting the lower end of Said cathode and said heater in spaced posip..

tion with respect to cach other, a fixed supporting member in said tube, means connecting said supporting member to the upper end of the heater to support the same, and additional means connecting said fixed member to as@ shown in Figa-'5VA 6, :a sliigihtlyfidifferent The members 52 and 54 have secured?.

The arms 72 and 74 are l.lo

the upper' end of the oathode'to support the same in spaced relation with respect to the heate'r, said rst connecting means having engagement with theixedv member at spaced points one on each side of the central transverse axis of the fixed member.

In testimony whereof I afx my signature.

ROBERT HARD'ING, JR. o 

